The Art of the Surface Interval: What is a surface interval and how do you master it?
After an intense but beautiful and memorable dive in the waters of Komodo National Park, you surface and wonder when you’re allowed to dive back into the blue. You look at your divemaster, he looks at his dive computer and tells you to climb up the stairs to enter the boat, sit back, relax and have a surface interval of at least 60 minutes. Why can’t we dive every hour of the day? Why is the human body not able to live amongst the fish that we love so deeply? And what do we do with the time we are not allowed to dive?
Breathing under pressure, why is it different?
Before we start, we like to refresh your mind with the basic physics of diving. The pressure of the water impacts the rate at which a diver’s body absorbs nitrogen while underwater. Remember the concept of atmospheres from your Open Water Course? During scuba training, you learned that this surface pressure is referred to as 1 atmosphere. When a diver enters the water, he needs only to descend to a depth of 10m in salt water before the pressure doubles. The pressure you will experience at this depth is 2 atmospheres, and the pressure increases by 1 atmosphere for every 10m of depth.
The air we breathe is a mixture of mostly nitrogen (79 percent) and oxygen (21 percent). When you inhale air, your body consumes the oxygen, replaces some of it with carbon dioxide, but does nothing with the nitrogen. At normal atmospheric pressure, some of the nitrogen and oxygen are dissolved in the fluid portions of your blood and tissues. But this is where it gets interesting. As you descend under the water, the pressure on your body increases. And when you increase pressure on a fluid (your body is approximately 60% water), you also increase the volume of gas it can absorb. Therefore, as you enjoy your dive, more gas is slowly dissolved into your body. The majority of the oxygen is consumed by your tissues, but the nitrogen remains dissolved.
The only way to reduce the amount of nitrogen in your blood is to remain out of the water between two dives, ascending slowly and doing a safety stop also benefits. During this time called “the surface interval”, the nitrogen absorbed during the first dive continues to “off-gas”, in other words, to be released from your body.
How do you know when you can dive again?
Once you reach the surface after a dive, your body is in its natural pressure and the tissue will release the stored nitrogen. Using your dive profile and your time at depth, you can start calculating the pressure group, and the time you must remain on the surface for the nitrogen in your blood to drop to an acceptable level. You should use this information to plan your next dive.
Using the Dive Table will tell you your minimum surface interval required between your dives. On most dives, a one-hour surface interval is standard. At this point, a substantial percentage of nitrogen has been released and the impact on a next dive is minimal.
If your first dive was deep and near the no decompression limit, with a second dive also deep, then it is recommended to wait two hours before your next dive. The extra time on the surface will give you a longer bottom time. If you are using a dive computer, placing it in plan mode will show you the information in real time.
So now I know the importance of the Surface Interval, what do I do with this time?
In addition to the off-gassing requirements, the surface interval can be used for other purposes. Since Komodo is a fairly large park, the time between your dives will be used to sail over to the next dive site. Also, while our crew will swap your old tank for your new tank, you can use this time to double check your gear.
Mild dehydration is common while diving and nothing to worry about. The air we breathe when diving has been dehumidified when we filled the tank. While underwater you do not sweat very much, as soon as you reach the surface that will change due to the tropical climate here in Komodo National Park.
So to prevent yourself from getting dehydrated, it’s wise to start with water or tea, which is always provided on our dive boats. Plan on slowly consuming at least a litre of water during your surface interval, more if you’re enjoying the soothing rays of the sun on our top deck.
Enjoy the stunning surroundings of Komodo National Park
Did you know that a tour around Komodo National Park will cost about 80 US dollars for a two-hour boat ride and another few hours of snorkeling? Since driving from one dive spot to the next during the surface interval is mandatory, you might as well enjoy the scenery that will surround you. The Jurassic Park-like landscapes will ease your mind as our boat gracefully glides over the azure blue waters.
There is a likely chance you will be granted with the sighting of marine life like dolphins and turtles, who sometimes seem to want to know what all the fuzz is about and check out our boats.
Re-energize your body
We take great pride in the quality of the food we provide on our boats. After an exhilarating dive, a light meal or a snack is an excellent way to restore your energy levels. Because eating goes hand in hand with staying hydrated, we will not serve salty foods like potato chips. Instead, we serve fruits and small snacks after your first dive, and a well-deserved nutritious lunch with rice, vegetables, added with a special homemade sauce after your second dive. But, we save the best for last. After your final dive, we serve our famous Belgium Waffles on our way back to Labuan Bajo, as you take place on our sundeck and enjoy the last warm rays of the slowly setting sun, you realize life is really not that bad.
Rest and Relax
Now the most important part of the surface interval, and what really makes it into an Art is resting and relaxing. Diving can deplete your energy levels, especially if you are flying through the famous currents of Komodo National Park. As such it is crucial that you rest your body for a while to recuperate. Because rest is not idleness.
To lie under the calming rays of the sun after a dive, listening to the murmur of the ocean, watching the clouds float across the sky, is the best way to recharge before another adventure in the deep.
We hope you now understand why it takes time for your body to reduce the amount of nitrogen in it. And since safety is our number one priority here at Manta Rhei, we hope that you understand why we take the surface interval so seriously, and we hope that you will too. Next time you are between dives, take a moment and try to think how you can master the art of the surface interval. It’s just like all fun things in life, you need to enjoy it responsibly.
So enjoy our luxurious sundeck, enjoy our delicious food and enjoy the magnificent Komodo National Park.